Electronic ignition delay for 5 38 and 5 54 rocket assisted projectiles

ABSTRACT

To provide reliable and accurate ignition timing for 5&#39;&#39;&#39;&#39;/38 and 5&#39;&#39;&#39;&#39;/54 rocket assisted projectiles, a mass is situated so as to shear loose its holding pin when the projectile is gun fired. At termination of setback, the mass is moved by a spring to percussively actuate the thermal battery. The battery provides power to a timing circuit which after a suitable delay switches current through a squib.

United States Patent 1191 Stout, Jr. et al. 1 1 Jan. 30, 1973 1541 ELECTRONIC IGNITION DELAY FOR 3,859,904 12/1967 Nerheim 102/702 GI 5"/38 AND 5"/54 ROCKET ASSISTED 2.827.851 5/1958 Ferrara ..102/70.2 o1 PROJECTILES 3,064,576 11/1962 Lytle ..102/70.21

3,363,566 I968 G' 0 [75] Inventors: Lilburn G. Stout, Jr., Falmouth; H mum at a] 1 2/70 2 Robe" Butler; Thomas Smith Primary Examiner-Benjamin A Borchelt I both of iiredencksburg of va- Assistan! Examiner-Thomas H. Webb Assignee: The United states of America as AttorneyR. S. Sciascia and Thomas 0. Watson, .lr.

represented by the Secretary of the r Navy 57 ABSTRACT [22] Wed: 1969 To provide reliable and accurate ignition timing for [2]] Appl. No.: 889,855 5"/38 and 5"/54 rocket assisted projectiles, a mass is situated so as to shear loose its holding pin when the 52 us. c1. ..102 70.2 A P' is terminal Setback 51 1111. c1 ..F42c ll/06, F426 11 00, F42C 9/00 mass is moved by a Spring to PercuS-Sively actuate the [58] Field 61 Search ..102/70.2 01, 70.2 1, 70.2 0, thermal y- The ry Provides Power to a l02/70.2 P UX, 70.2 ing circuit which after a suitable delay switches current through a squib. 56 References Cited I 5 Claims, 2 Drawing Figures UNITED STATES PATENTS 3,094,932 6/1963 Greenlees 102/7021 l6 l4 l5 PAIENTEDmso I975 INVENTORS LILBUR/V a. sraurum ATTORNEYS ROBERT F. Burden BY THOMAS 5'. SMITH I fin. 0, 0%

FIG. 2

ELECTRONIC IGNITION DELAY FOR "l38 AND 5 "/54 ROCKET ASSISTED PROJECT ILES STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION This invention pertains to a timed ignition delay system for projectiles, and more specifically to an electronic ignition delay system for 5"/38 and 5"/54 rocket assisted projectiles. Prior art delay systems utilize a pressure actuated belville washer to initiate a pyrotechnic delay train which in turn initiates a rocket assist motor. This type of system is comparatively unreliable in that debris associated with gun pressure cause failures in the delay train initiation. Further the pyrotechnic delay train is temperature sensitive and may cause an initiation time spread of up to 4 sec. in 20, over a temperature range of +20 to +120F.

SUMMARY OF THE INVENTION The present invention, by utilizing solid state electronics and mechanical actuation means obviates the problems of initiation time spread and debris percipitation associated with present state of the art systems and further, provides an ignition delay system that has an indefinite shelf life. A mass which is held in position by a frangible pin is spring biased so that upon set back occuring at launch, the holding pin is sheared causing the mass to be freed. As the projectile accelerates to the peak of its trajectory, the mass is moved downwardly so that the biasing spring is further compressed. Upon deceleration occuring, the spring tends to move the mass in the direction of a thermal battery. The battery is actuated upon contact with the mass. whereupon, the solid state timing circuit which comprises passive and active circuit elements sets its inherent time delay into effect. Upon termination of such delay, the timing circuit sends a current through a squib which actuates the charge in the projectile.

OBJECTS OF THE INVENTION An object of this invention is to provide a more reliable ignition system for projectiles.

A further object of this invention is to provide a more reliable ignition system for rocket assisted projectiles.

A still further object of this invention is to provide a more accurate and reliable ignition system for existing rocket assisted projectiles.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates, diagrammatically, the arrangement of the various components of the invention;

FIG. 2 illustrates, schematically, the timing circuit which forms part of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a cross-section of housing 10 is taken to show a possible arrangement of the various components of the invention within that housing. Base portion 11 would be physically connected to the projectile or the rocket assist motor of the projectile. Casing 12 therefore, would be located within the projectile or the rocket assist motor, in such a manner that initiation of the charge 22 would actuate the rocket assist motor. The movable mass 14 is located within base portion 11. Mass 14 is fastened into a stationary position by pin 15 which may be threaded into mass 14 through a recess 17 in base portion 11. Spring 13 is located beneath mass 14 so that when set back occurs, mass 14 will be acted upon, by the momentum forces caused by acceleration, to shear pin 15 and move mass 14 downwards so as to compress spring 13. When the acceleration forces, initially occuring at launch, decrease, mass 14 will be forced upward by the energy stored in spring 13 so that contact hammer 16 comes into contact with thermal battery 18. Such contact will actuate thermal battery 18 in a manner that is well known to those of ordinary skill in the art. For example, the hammer 16 may contact a percussion primer. The heat produced by the primer will actuate the thermal battery. 1f the heat produced by the primer is inadequate, a Thermite (trademark) may be placed between the primer and the battery. The heat produced by the Thermite (trademark) will then actuate the battery. Upon actuation of battery 18, the timing circuit 19 which is connected to battery 18 begins its timing cycle. After such timing cycle has run, a current is passed through squib 20 causing it to detonate and it in turn detonates ignition charge 22 which will actuate the rocket assist motor.

Referring now to FIG. 2 which illustrates a timing circuit that may be used with the invention. Thermal battery 18 is schematically illustrated as being connected directly across resistor 26 and capacitor 27 which forms an RC time circuit. Upon thermal battery 18 being actuated, a certain time delay occurs because of the charging of capacitor 27 through resistor 26. After capacitor 27 reaches a full charge, transistor 28, which will have been biased by resistors 29 and 30 to conduct upon capacitor 27 reaching a full charge, will conduct and inject a control voltage into thyratron transistor 31 causing it to go into its closed circuit state. Upon thyratron transistor 31, which may be a silicon controlled rectifier, switching to its closed circuit state, squib 34, in effect, will beplaced across thermal battery 18 in parallel with the branches containing resistors 29, 30 and resistor 26, capacitor 27. Such a placement of squib 34 into the battery circuit will cause sufficient current to flow through squib 34 to initiate it.

A list of components that have been successfully used in the timing circuit followsBattery 18 may be a 2] volt catalyst research battery. Squib 34 may be a Dupont S type. Resistor 26 may be a 1.69 megohm, one-half watt 1 percent Sprague metal film resistor. Resistor 29 may be a 4.99 K ohms, one-half watt 1 percent Corning. Capacitor 27 may be a 10 microfarad 10 volt Sprague. Transistor 28 may be any one of the well known transistors in the art that will function in the manner described. Thyratron transistor 31, may be a silicon controlled rectifier type.

As described in regard to FIG. 1 the components of the invention, such as the timing circuit of FIG. 2, the initiation means, battery and squib, are all enclosed within casing 10 which is a form and size that is compatible with existing, state of the art, 5"/38 and 5"/54 rocket assisted projectiles. This compatibility permits replacing the present pressure actuated belville pyrotechnic delay train with casing and its contents. Because of the components used, the housing 10 may take on various other shapes which would be compatible with further projectile designs of larger or smaller size.

It must be understood that additional safety devices may be added between the battery and the electronic circuit which can take the form of centrifugal or setback switches. These safety devices would enhance the handling safety of a projectile using this type of ignition system.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings.

What is claimed is:

1. An ignition system for rocket assisted projectile comprising:

a housing;

a spring disposed within said housing at one end thereof;

a pin disposed, adjacent said one end of said housing, partly within said housing and partly within a wall of said housing;

means, disposed at said one end of said housing so as to move within said housing, for shearing the pin and compressing the spring by moving in a first direction when the projectile is accelerating and for actuating a battery by moving, under force of the spring, in a second direction directly opposite to said first direction when the projectile ceases to accelerate;

a battery disposed within said housing and within the path of movement of said means so as to be actuated by said means;

a timing circuit disposed within said housing and powered by said battery so as to provide a predetermined time delay upon actuation of said battery;

a squib disposed within said housing electrically connected to the timing circuit so as to be activated by said battery at the end of said time delay;

a charge disposed adjacent said squib and detonated thereby.

2. The ignition system of claim 1 wherein the housing includes a base portion at said one end, the base portion comprising means for connecting the housing to the projectile.

3. The ignition system of claim 1 wherein said battery is a thermal battery.

4. The ignition system of claim 1 wherein said timing circuit comprises solid state active circuit elements.

5. The ignition system of claim 4 wherein said battery is a thermal battery that will be initiated upon percussive contact by a mass. 

1. An ignition system for rocket assisted projectile comprising: a housing; a spring disposed within said housing at one end thereof; a pin disposed, adjacent said one end of said housing, partly within said housing and partly within a wall of said housing; means, disposed at said one end of said housing so as to move within said housing, for shearing the pin and compressing the spring by moving in a first direction when the projectile is accelerating and for actuating a battery by moving, under force of the spring, in a second direction directly opposite to said first direction when the projectile ceases to accelerate; a battery disposed within said housing and within the path of movement of said means so as to be actuated by said means; a timing circuit disposed within said housing and powered by said battery so as to provide a predetermined time delay upon actuation of said battery; a squib disposed within said housing electrically connected to the timing circuit so as to be activated by said battery at the end of said time delay; a charge disposed adjacent said squib and detonated thereby.
 1. An ignition system for rocket assisted projectile comprising: a housing; a spring disposed within said housing at one end thereof; a pin disposed, adjacent said one end of said housing, partly within said housing and partly within a wall of said housing; means, disposed at said one end of said housing so as to move within said housing, for shearing the pin and compressing the spring by moving in a first direction when the projectile is accelerating and for actuating a battery by moving, under force of the spring, in a second direction directly opposite to said first direction when the projectile ceases to accelerate; a battery disposed within said housing and within the path of movement of said means so as to be actuated by said means; a timing circuit disposed within said housing and powered by said battery so as to provide a predetermined time delay upon actuation of said battery; a squib disposed within said housing electrically connected to the timing circuit so as to be activated by said battery at the end of said time delay; a charge disposed adjacent said squib and detonated thereby.
 2. The ignition system of claim 1 wherein the housing includes a base portion at said one end, the base portion comprising means for connecting the housing to the projectile.
 3. The ignition system of claim 1 wherein said battery is a thermal battery.
 4. The ignition system of claim 1 wherein said timing circuit comprises solid state active circuit elements. 